Photographic diffusion transfer process



April 1963 w. H. RYAN ETAL 3,087,815

PHOTOGRAPHIC DIFFUSION TRANSFER PROCESS Filed April 22, 1959 SPREADERSHEET COMPOSITION PHOTOSENSITIVE LAYER IMAGE-RECEIVING LAYER CONTAININGDEACETYLATED CHITIN SUPPORT FIG.I

SUPPORT PHOTOSENSITIVE LAYER PROCESSING COMPOSITION MAGE-RECEIVING LAYERCONTAINING DEACETYLATED CHITIN --FIG.2

TRANSPARENT SUPPORT COLOR SCREEN ELEMENT IMAGE-RECEIVING LAYERCONTAINING DEACETYLATED CHITIN PHOTOSENSITIVE LAYER FIG.3 I

SUPPORT LAYER CONTAINING IMAGE-FORMING COMPONENTS PHOTOSENSITIVE LAYERRUPTURABLE CONTAINER IMAGE-RECEIVING LAYER CONTAINING DEACETYLATEDCHITIN FIG.4

ATTORNEYS United States Patent Office Patented Apr. 30, 1963 3,087,815PHOTOGRAPHIC DIFFUSION TRANSFER PROCESS William H. Ryan, Carlisle, andElizabeth L. Yankowslri, Watertown, Mass., assignors to Polaroid(Iorporation, Cambridge, Mass., a corporation of Delaware Filed Apr. 22,1959, Ser. No. 808,123 4 Claims. (Cl. 96-3) This invention relates tophotography and, more particularly, to novel photographicdiflfusion-transfer processes and products for utilization therein.

It is one object of the present invention to provide noveldiffusion-transfer processes and products for utilization thereinwhereby improved positive silver images may be produced.

Another object of the present invention is to provide noveldiffusion-transfer processes and products for utilization thereinwhereby improved additive color reproduction may be attained.

A further object of the present invention is to provide noveldiffusion-transfer processes and products for utilization thereinwhereby improved subtractive color reproduction may be attained.

A still further object of the present invention is to provide novelphotographic products and processes wherein a positive diiiusion-tranferimage is disposed in a single stratum, self-sustaining, dimensionallystable image-receiving element.

A still further object of the present invention is to provide novelphotographic products and processes wherein a positivediffusion-transfer image is disposed in an image-receiving stratumexhibiting increased resistance to abrasion.

A still further object of the present invention is to provide novelphotographic products and processes Wherein an image-receiving elementfor use in monochromatic and/or multichromatic diffusion-transferprocesses comprises, at least in part, a mordant for soluble dyestransferred thereto.

Other objects of the present invention will in part be obvious and willin part appear hereinafter.

The invention accordingly comprises the several steps and the relationand order of one or more of such steps with respect to each of theothers, and the product possessing the features, properties and therelation of elements which are exemplified in the following detaileddisclosure, and the scope of the application of which will be indicatedin the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing wherein:

FIGURE 1 is a diagrammatic enlarged cross-sectional View illustratingthe association of elements during one stage of the performance of adiffusion-transfer process for the production of positive silver printsand showing, as one of the elements, an embodiment of the novelprintreceiving elements of the present invention, the thicknesses of thevarious materials being exaggerated;

FIG. 2 is a view similar to that of FIG. 1 illustrating the associationof elements during one stage of the performance of anotherdiiiusion-transfer process for the production of positive silver printswhich illustrates another embodiment of the novel print-receivingelements of the present invention;

FIG. 3 is a diagrammatic enlarged cross-sectional view of one embodimentof the novel image-receiving elements of the present invention, for usein obtaining additive multicolor images, comprising a support, anadditive color screen element, an embodiment of the present invention asthe image-receiving stratum, and a photosensitive silver halideemulsion; and

FIG. 4 is a diagrammatic enlarged cross-sectional view of one embodimentof the novel image-receiving elements of the present invention, for usein obtaining subtractive color images, comprising a photosensitiveelement which comprises a support, a layer containing color imageformingcomponents and a photosensitive silver halide emulsion, a rupturablecontainer, and an embodiment of the present invention as theimage-receiving element.

The present invention comprehends improved processes and products of thetype whereby a positive print is obtained in a single step by suitablytreating an exposed photosensitive element, containing a latent imagetherein, in superposed relationship to an appropriate image-receivingelement with a processing composition.

In diffusion-transfer processes, for the formation of positive silverimages, a latent image contained in an exposed photosensitive silverhalide emulsion is developed and almost concurrently therewith a solublesilver complex is obtained by reaction of a silver halide solvent withthe unexposed and undeveloped silver halide of said emulsion.Preferably, the photosensitive silver halide emulsion is developed witha processing composition in a 'viscous condition which is spread betweenthe photo sensitive element comprising the silver halide emulsion, and aprint-receiving element comprising, preferably a suitable silverprecipitating layer. The processing composition eliects development ofthe latent image in the emulsion and substantially contemporaneoustherewith forms a soluble silver complex, for example, a thiosulfate orthiocyanate, with undeveloped silver halide. This soluble silver complexis, at least in part, transported in the direction of theprint-receiving element and the silver thereof is largely precipitatedin the silver precipitating layer of said element to form a positiveimage therein.

Additive color reproduction may be produced by exposing a photosensitivesilver halide emulsion through an additive color screen having filtermedia or screen elements each of an individual additive color, such asred or blue or green, and by viewing the reversed or positive silverimage formed by transfer to a transparent, print-receiving elementthrough the same or a similar screen which is suitably registered withthe reversed positive image carried by the print-receiving layer.

The copending application of Howard G. Rogers, Serial No. 748,421, filedJuly 14, 1958 (a continuationin-part of Serial No. 415,073, filed March9, 1954 and now abandoned), discloses and claims diflusion-transferprocesses wherein initially mobile and ditfusible dye developers, thatis, complete dyes which contain in the same molecular structure a silverhalide developing function, are utilized in the development of a latentimage present in an exposed photosensitive silver halide emulsion,effecting thereby immobilization of said dye developers in saidphotosensitive emulsion as a function of the point-to-point degree ofexposure thereof, and transferring at least part of the imagewisedistribution of mobile dye developer from the unexposed areas of saidphotosensitive emulsion, by imbibition, to a superposed image-receivinglayer or element to impart thereto a color transfer image.

United States Patents Nos. 2,647,049, issued July 28, 1953, 2,661,293,issued December 1 1953, 2,698,244, issued December 28, 1954, 2,698,798,issued January 4, 1955, and 2,802,735, issued August 13, 1957, all inthe name of Edwin H. Land, disclose diffusion-transfer processes whereincolor coupling techniques are utilized to provide color images.Image-forming components comprising one or more color developing agentsand one or more color formers or couplers are reacted to provide Q apositive color image to a superposed image-receiving element.

It has now been discovered that diffusion-transfer processes such asthose mentioned above may be substantially improved by use ofdeacetylated chitin in the printreceiving medium.

The term deacetylated chitin as utilized herein is intended to signifythe product prepared by removing in whole or in part the acetyl groupsfrom the polymeric acetamido derivative of a carbohydrate technicallydesignated as chitin. It is also intended to include any other productsubstantially identical therewith, as for example, where such product isproduced synthetically.

The presence of deactylated chitin in the image-receiving layerprovides, subsequent to contact of said chitin with alkali, as forexample, an alkaline photographic processing composition, asubstantially water-insoluble, abrasion-resistant matrix which may besubstantially flexible, semi-rigid, or rigid depending upon theconcentration of deacetylated chitin contained in said image-receivingelement. In addition, the deacetylated chitin affords substantialprotection to the positive image. An image-receiving layer comprising,at least in part, deacetylated chitin may be washed, for example, toeffect demoval of a photosensitive emulsion and/ or film-formingprocessing composition adhering thereto, or residual, undesired reagentsremaining therein, without deleterious effects. Where desirable, theconcentration of chitin disposed in the print-receiving element may beof sufficient magnitude to provide an integral single layer elementexhibiting suflicient internal support as to substantially alleviate thenecessity of providing one or more separate supporting layers.

The concentration of deacetylated chitin disposed in the image-receivinglayer may be varied over a wide range according to the degree ofrigidity desired, during and subsequent to processing, and the thicknessand character of the image-receiving stratum employed.

The image-receiving layer in addition to the deacetylated chitincontained therein may itself be comprised of one or more strata of apermeable material dyeable from a photographic processing composition.As examples of image-receiving materials of a dyeable nature, mentionmay be made of: regenerated cellulose; polyvinyl alcohol; partiallyhydrolyzed polyvinyl acetate; sodium alginate; cellulose ethers, such asmethyl cellulose or other cellulose derivatives such as sodiumcarboxymethyl cellulose or hydroxyethyl cellulose; papers; proteins,such as gelatin or glue; carbohydrates, such as gums and starches; andmixtures of such materials, as for example, polyvinyl alcohol andgelatin, Where they are compatible. Gelatin comprises a preferredimage-receiving material.

Referring now to FIG. 1, one embodiment of the novel image-receivinglayers of the present invention in the performance of a transfer processfor the production of positive silver prints comprises a spreader sheeta layer of relatively viscous processing agent 11, a photosensitivesilver halide emulsion layer 12, an image-receiving layer 13 containingdeacetylated chitin and preferably containing silver precipitatingnuclei, such as the silver precipitating nuclei disclosed in UnitedStates Patent No. 2,698,237, issued December 28, 1954, to Edwin H. Land,and a suitable support layer 14. Support layer 14 may comprise an opaquematerial where a reflection print is desired or may comprise atransparent material where a transparency is desired.

Liquid layer 11 may be obtained by spreading a photographic processingcomposition, for example, in a manner disclosed in U.S. Patent No.2,698,244, issued December 28, 1954, to Edwin H. Land. As disclosed inthe aforementioned U.S. patent, the liquid processing composition may bedisposed in a rupturable container so positioned in regard to theappropriate surface of the silver halide emulsion that, upon compressionby spreader sheet 10, a substantially uniform layer 11 of processingcomposition is distributed over the surface of said photosensitiveemulsion 12, positioned distally from the deacetylated chitin-containingimage-receiving layer 13. The processing composition may be one of thefilm-forming processing compositions disclosed in U.S. Patent No.2,543,181, issued February 27, 1951, to Edwin H. Land. It may comprise,for example, a developing agent such as hydroquinone, an alkali such assodium hydroxide, a silver halide complexing agent such as sodiumthiosulfate, and a high molecular weight film-forming thickening agentsuch as sodium carboxymethyl cellulose. All these materials arepreferably in aqueous solution. These photographic agents are preferablycontained in solution in the processing liquid prior to the spreadingthereof as layer 11, but they may be in part or wholly added to theprocessing composition as it is spread between spreader sheet 10 andphotosensitive silver halide emulsion 12, said agents being so locatedon or adjacent to the surface of one or both of said layers as to bedissolved by or otherwise interacted with the liquid agent when thelatter wets said surface.

In carrying out the aforementioned transfer process, the photosensitivesilver halide emulsion 12 is exposed to a predetermined subject matterto form therein a latent image of said subject matter. A substantiallyuniform distribution of processing composition 11 is distributed on theexternal surface of said emulsion, as for example, according to thepreviously described procedure. Processing composition reagents permeateinto the photosensitive emulsion, developing the latent image containedtherein according to the point-to-point degree of exposure of saidemulsion. Substantially contemporaneous with the development of thelatent image, an imagewise distribution of soluble silver complex isformed from unexposed silver halide within said emulsion. At least partof said silver complex, solubilized, is transferred, by inbibition, tothe deacetylated chitin-containing print-receiving stratum 13. Thetransferred silver complex is reacted to provide a positive, reversedimage of the latent image. Subsequent to formation of the positive imagein the deacetylated chitin-containing image-receiving layer 13,dissociation of said layer from emulsion layer 12 may be effected.

Where desired, the deactylated chitin-containing imagereceiving layer 13may be dissociated from emulsion layer 12 by washing the emulsion fromthe surface thereof with water. It must be noted that theabrasion-resistant properties provided image-receiving element 13 by theinclusion therein of deactylated chitin alleviates the necessity ofsubsequently overcoating the external surface of imagereceiving layer 13with a transparent abrasion-resistant water-insoluble plastic to preventsubsequent laceration and resultant degradation of the positive image.

The fabrication of the novel print-receiving elements of the presentinvention will be illustrated in greater detail in conjunction with thefollowing specific example which sets out a representativeimage-receiving element and the utilization thereof in adiffusion-transfer process of the last-mentioned type. This example isintended to be illustrative only.

Example 1 A mixture comprising cc. of water, 011 gram of deacetylatedchitin and 1 cc. glacial acetic acid is blended in a Waring Blendor.0.12 g. of silver acetate is dispersed in the resultant blend to providephotographic silver precipitating nuclei.

A print-receiving element is prepared by coating a surface hydrolyzedcellulose acetate base with the blend. After this coating has dried, asilver iodobromide emulsion is applied. The photosensitive emulsion isexposed and processed by spreading an aqueous liquid processingcomposition, such as described in the aforementioned U.S. Patent No.2,543,181, on the external surface of the photosensitive emulsion. Afteran imbibition period of approximately one minute, the image-receivingelement is stripped from the emulsion and contains a positive transferimage of the photographed subject.

In the aforementioned example, spreading of the liquid processingcomposition on the external surface of the photosensitive emulsion ispreferably effected by rupture of a suitably positioned frangiblecontainer and distribution of its processing composition contents bymeans of a converted cellulose acetate spreader sheet, i.e., a celluloseacetate sheet the surface of which has been converted to cellulose. Whenemployed in Example 1, the converted cellulose acetate spreader sheetexhibited an adhesive capacity for the processing composition in excessof the adhesive capacity exhibited by the photosensitive emulsion. Ameans is thus provided for effecting dissociation of the processingcomposition from contact with the photosensitive emulsion, preferablysubsequent to image formation, by dissociating the spreader sheet fromits proximate relationship to the external emulsion surface.

It will be apparent that the facility with which the photosensitiveemulsion layer is dissociated from contact with the deaceylated chitinprint-receiving element may be increased by providing a conventionalstripping layer interposed between said emulsion and the print-receivingelement. The stripping layer may be coated on the surface of theprint-receiving element and the photosensitive emulsion thereaftercoated on the external surface of said stripping layer.

A further embodiment of the present invention is illustrated in FIG. 2,which comprises a photosensitive silver halide emulsion 12, a layer 11of the previously noted relatively viscous film-forming processingcomposition, and an image-receiving layer 20 containing a sufficientconcentration of deaceylated chitin to provide a self-sustaining,dimensionally stable, rigid, semi-rigid or flexible film, and preferablycontaining silver precipitating nuclei.

As previously stated, layer 11 of processing composition may bedistributed in a substantially uniform manner between photosensitiveemulsion layer 12 and imagereceiving layer 20, for example, inaccordance with the procedures disclosed in the aforementioned U.S.Patent No. 2,543,181. For example, one or more rupturable containers maybe attached to either photosensitive emulsion layer 11 and/orimage-receiving layer 20 such that upon superposition of the respectivelayers 11 and 20' said container or containers are so positioned as tobe capable, upon rupture, of releasing their contents in a substantiallyuniform layer between and in contact with the opposed surface of each ofsaid layers. Rupture of the container or containers are spreading of thecontents thereof may be accomplished, for example, by compressionbetween a pair of opposed, suitably gapped, rollers.

In carrying out the aforementioned transfer process, the photosensitivesilver halide emulsion 12 is exposed to a predetermined subject matterto form therein a latent image of said subject matter. The exposedemulsion is superposed on the deacetylated chitin-containingimagereceiving element 20 and the photographic processing composition 11spread between the opposed surfaces of said photosensitive emulsion 12and said image-receiving element 20. Reagents permeate into thephotosensitive emulsion 12, developing the latent image containedtherein and forming a soluble silver complex of unexposed silver halide.Soluble silver complex is transported from photosensitive emulsion layer12, at least in part, by imbibition, to the deacetylatedchitin-containing print-receiving stratum 20 and the silver of thecomplex is precipitated thereon to provide the desired positive image.The lamination formed by the spreading of processing composition inlayer 11 between photosensitive emulsion 12 and printreceiving element26 is kept intact for approximately /2 to 1 /2 minutes, preferably 1minute, and at the termination of this time interval the deacetylatedchitin-containing print-receiving layer 2%) is dissociated from emulsion12, as for example, by stripping.

The following examples illustrate the fabrication of additionalprint-receiving elements of the present invention and the utilizationthereof in diffusion-transfer processes of the last-mentioned type,which however, are not limited to the details therein set forth and areintended to be illustrative only.

Example 2 Deacetylated chitin and gelatin are each separately treated byevaporating gold onto the surface of flakes or particles thereof, inaccordance with the vacuum deposition procedures disclosed in thecopending US. application of Edwin H. Land, Serial No. 705,845, filedDecember 30, 1957, to provide photographic silver precipitating nuclei.

A print-receiving element is prepared by coating a cellulose acetatesupport, whose surface has been hydrolyzed, with a 1% acetic acidsolution comprising a mixture of 2 grams each of the deacetylated chitinand gelatin described above. After this coating has dried, a celluloseacetate hydrogen phthalate stripping layer is applied.

A photosensitive element is exposed and processed by spreading anaqueous liquid processing composition comprising:

between said photosensitive element and the print-receiving element,prepared above, as said elements are brought into superposedrelationship. After an imbibition period of approximately one minute,the print-receiving element is separated and contains a positivetransfer image of the photographed subject. This print could be washedin running water without deleterious effects.

Example 3 A print-receiving element is prepared by coating a celluloseacetate support, of the type disclosed in Example 2, with a mixturecomprising 5 parts polyvinyl alcohol and 1 part deacetylated chitin,each of which components had previously been treated by evaporativedeposition of gold onto flakes or particles thereof, to provide silverprecipitants, according to the procedure disclosed in Example 2. Afterthis coating has dried, a cellulose acetate hydrogen phthalate strippinglayer is applied thereon.

The resultant print-receiving element is employed in thediffusion-transfer process of Example 2 to provide a positive transferimage thereon.

The procedures of Examples 2 and 3 provide positive transparencies whichdo not have to be subjected to hardening treatments after stripping. Inaddition, it is possible to wash such images after an extended intervalto remove residual developer traces.

Example 4 A print-receiving element is prepared by coating a celluloseacetate-coated'paper base with a 1% acetic acid solution containing 1gram of the treated deacetylated chitin and 1 gram of the treatedgelatin described in Example 2, to give an image-receiving layerapproximately one-half as thick as that in Example 1. After this coatinghas dried, a cellulose acetate hydrogen phthalate stripping layer iscoated thereon.

The resultant print-receiving element is employed in thediffusion-transfer process of Example 2 to provide a positive transferimage thereon.

As illustrated in FIG. 3, one embodiment of the present invention foruse in additive multicolor diffusiontransfer processes is a compositefilm unit comprising a transparent support 30, an additive color screenelement 31, an image-receiving layer 13 containing deaceylated chitinand preferably containing silver precipitating nuclei, and aphotosensitive silver halide emulsion 12.

In carrying out an additive multicolor diffusion-transfer processutilizing the aforementioned composite film unit, exposure of thephotosenstive silver halide emulsion to a predetermined subject matteris effected through color screen element 31. A liquid processingcomposition is applied to photosensitive emulsion 12, as for example,according to the procedure previously described in explanation ofFIG. 1. The liquid processing composition permeates into photosensitiveemulsion 12, developing the latent image contained therein, forming animagewise distribution of soluble silver complex in the unexposed areasthereof, and transferring, at least part of said imagewise distribution,by imbibition, toward image-receiving layer 13 wherein the silver ofsaid complex is precipitated to provide a reversed positive silver imageof said latent image. Dissociation of emulsion layer 12 fromimagereceiving layer 13 may be accomplished, for example, according tothe procedure previously described in explanation of FIG. 1. Aspreviously stated, in additive multicolor processes the viewing of thepositive image takes place through a stationarily registered colorscreen element, either that screen element through which exposure wasaccomplished or a duplicate thereof. Although in the aforementionedprocess exposure is accomplished through the stationary color screenelement predisposed in the image-receiving element, thus avoiding theproblems incident upon attempts to register a mobile screen element withthe deposited silver image, it must be noted that the inventive conceptof the present specification is equally applicable to the numerousadditive multicolor diifusion-transfer processes utilizing color screenelements in combination with silver transfer processes, such as, forexample, the additive multicolor transfer processes disclosed in US.Patent No. 2,614,926, issued October 21, 1952, to Edwin H. Land.

US. Patent No. 2,707,150, issued April 26, 1955, to Edwin H. Land,discloses additive multicolor processes utilizing a color screen elementin a photosensitive emulsion wherein, subsequent to the selectiveexposure of the photosensitive emulsion through said color screen andsubstantially simultaneous with the development of the latent imagecontained therein, the color screen element filter media, preferablysoluble dyes, transfer, at least in part, by imbibition to animage-receiving element to form therein a substantially duplicate screenpattern of the original color screen. In the practice of this procedureutilizing an image-receiving layer comprising chitin, the deacetylatedchitin exhibits the properties of a mordant for numerous of thepotentially available soluble dyes utilized as filter media.

The following examples illustrate the fabrication of additionalprint-receiving elements of the present invention and the utilizationthereof in additive multicolor diffusion-transfer processes, which,however, are not limited to the details therein set forth and areintended to be illustrative only.

Example An additive multicolor print-receiving element is prepared bycoating a Dufay color film base, which comprises a transparent plasticsupport having a preformed additive color screen thereon, with thedeacetylated chitin/silver acetate blend of Example 1. After thiscoating has dried, a silver iodobromide emulsion is applied thereon.This photosensitive emulsion is exposed through the transparent supportand additive color screen. The exposed emulsion is processed byspreading a liquid processing composition such as that set forth inExample 2 on the external surface of the said emulsion. After animbibition period of approximately one minute, the emulsion is separatedfrom the deacetylated chitin-containing print-receiving layer whichcontains a positive transfer image of the photographed subject.

Viewing of the multicolor additive positive transfer image takes placethrough the transparent base and preformed additive color screen throughwhich exposure was accomplished.

Example 6 An additive multicolor print-receiving element is prepared bycoating a Finlay plate, which comprises a transparent glass supporthaving a preformed additive color screen thereon, with the deacetylatedchitin/ silver acetate blend of Example 1. A photosensitive silveriodobromide emulsion is applied thereon, exposed, processed and viewedaccording to the procedure of Example 5.

In the following illustrative description of FIG. 4, the termimage-forming components is intended to signify the dye image precursorsutilized in the previously noted color coupling and dye developerdiffusion-transfer techniques, as well as the coupling dye techniquesdisclosed in US. Patent No. 2,774,668, issued December 18, 1956, toHoward G. Rogers, and in the copending US. application of Howard G.Rogers, Serial No. 613,691, filed October 3, 1956, to providemonochromatic or multichromatic subtractive color image formation.

FIG. 4 of the accompanying drawing illustrates one method of processinga photosensitive silver halide emulsion to obtain a subtractive colortransfer image in accordance with this invention. A photosensitiveelement 42 comprises a support 14, a layer 40 containing at least onecolor image-forming component, preferably at least one dye developer,and a photosensitive silver halide emulsion layer 12. As shown in theparticular embodiment depicted in FIG. 4, the photosensitive element isshown in a spread-apart relationship (as, for example, during exposure)with an image-receiving layer 20 containing deacetylated chitin havingmounted thereon a rupturable container 41 holding a processingcomposition. After exposure, the image-receiving element 20 containingdeacetylated chitin is brought into superposed relationship with thephotosensitive element and the rupturable container 41 is ruptured byapplication of suitable pressure, for example, by advancing between apair of rollers (not shown), and a layer of the liquid processingcomposition is spread between the superposed elements. The processingcomposition permeates the photosensitive silver halide emulsion layer 12and layer 40 containing image-forming components providing at least onesubtractive color. In exposed areas of the photosensitive element thecolor image-forming components, at least to some extent, exhibitdecreased solubility in contradistinction to unexposed areas. Thus, inunexposed areas, the color imageforming components will transfer, atleast in part, by imbibition, to the superposed image-receiving element20 to form thereon a positive image in terms of said unexposed areas.The image-receiving element 20 may be separated from a superposedrelationship with the photosensitive element after at least a portion ofthe colorforming components has been transferred.

It is also contemplated to utilize, in the preparation of subtractivecolor images, a film structure similar to FIG. 1, wherein the silverhalide emulsion is coated over the image-receiving layer and theprocessing composition must permeate through the emulsion beforereaching the image-receiving layer.

Multicolor images may be obtained using color-forming components anddiffusion-transfer processes by several techniques. One such techniquecontemplates the use of a photosensitive stratum comprising at least twosets of selectively sensitized, minute, photosensitive elements arrangedin the form of a photosensitive screen. Transfer processes of this typeare disclosed in the aforementioned copending US. application of HowardG. Rogers, Serial No. 748,421. In such an embodiment, each of the minutephotosensitive elements has associated therewith appropriate colorimage-forming components in or behind the silver halide emulsionportion. In general, a suitable photosensitive screen, prepared inaccordance with the disclosures of the last-mentioned copendingapplication, comprises minute red-sensitized emulsion elements, minutegreen-sensitized emulsion elements and minute bluesensitized emulsionelements arranged in side-by-side relationship in a screen pattern andhaving associated therewith, respectively, cyan color image-formingcomponents, magenta color image-forming components, and yellow colorimage-forming components.

Another process for obtaining multicolor transfer images utilizingcolor-forming components employs an integral multilayer photosensitiveelement wherein at least two selectively sensitized photosensitivestrata are superposed on a single support and are processed,simultaneously, and without separation, with a single, commonimage-receiving layer. A suitable arrangement of this type comprises asupport carrying a red-sensitive emulsion stratum, a green-sensitiveemulsion stratum and a blue-sensitive emulsion stratum, said emulsionshaving associated therewith, respectively, cyan color image-formingcomponents, magenta color image-forming components and yellow colorimage-forming components. The color image-forming components may beutilized in the emulsion layer, for example, in the form of particles,or one or more may be employed, respectively, as a layer behind theappropriate silver halide emulsion strata. Each set of emulsion andassociated color-forming components may be separated from the other setsby suitable interlayers, for example by a layer or layers of gelatin orpolyvinyl alcohol.

A further technique for obtaining multicolor images employs a pluralityof photosensitive elements associated with appropriate numbers ofimage-receiving elements and adapted to be treated with one or moreliquid processing compositions, the appropriate color image-formingcomponents being incorporated in the photosensitive elements. Examplesof film structures of this type are disclosed in the previously citedUS. Patent No. 2,647,049.

While a rupturable container, such as container 41 in FIG. 4, provides aconvenient means for spreading a liquid processing composition betweenlayers of a film unit whereby to permit the processing to be effectedwithin a suitable camera apparatus, the processes of this invention maybe otherwise effected. For example, a photosensitive element, afterexposure in suitable apparatus and while preventing further exposurethereafter to act-inic light, may be removed from such apparatus andpermeated with the liquid processing composition 1 as by coating thecomposition on said photosensitive element or otherwise wetting saidelement with the composition, following which the permeated, exposed,photosensitive element, still without additional exposure to actiniclight, is brought into contact with the image-receiving element forimage formation in the manner heretofore described. Details of suchrupturable containers as illustrated in FIG. 2 may be found in UnitedStates 'Patent No. 2,634,886, issued April 14, 1953, to Edwin H. Land.

As previously stated, the utilization of an image-receiving elementcomprising deacetylated chitin exhibits the additional advantageousproperty in that said chitin exhibits the properties of a mordant fornumerous of the potentially available color image-forming components,for example, color image-forming components such as dye developers,color couplers, coupling dyes, etc.

Since certain changes in carrying out the above process, and certainmodifications in the products which embody the invention, may be madewithout departing from its scope, it is intended that all mattercontained in the above description or shown in the accompanying drawingshall be interpreted as illustrative only and not in a limiting sense.

What is claimed is:

1. A process of forming silver diffusion transfer images which comprisesthe steps of developing an exposed photosensitive silver halide emulsionby contact of said emulsion with an aqueous alkaline processing solutionwhich includes a silver halide developing agent and a silver halidesolvent; contacting unexposed and undeveloped silver halide therein withsaid silver halide solvent and 'forming thereby an imagewisedistribution of soluble silver complex in unexposed areas of saidemulsion, as a function of the point-to-point degree of exposurethereof; transferring from said emulsion, at least in part, byimbibition, said imagewise distribution of soluble silver complex to animage-receiving layer containing silver precipitation nuclei positionedin superposed relationship with said emulsion, said image-receivinglayer containing deacetylated chitin in a concentration sufficient torender said image-receiving layer substantially water insoluble uponreaction of said deacetylated chitin with said aqueous alkalineprocessing solution; and there precipitating said silver complex toprovide thereby a silver transfer image.

2. A process as defined in claim 1, wherein an additive color screen ispositioned between said image-receiving layer and a support for saidimage-receiving layer, and exposure of said photosensitive emulsion isefiected through said additive color screen.

3. A process as defined in claim 1, wherein said imagereceiving layercomprises deacetylated chitin, silver precipitation nuclei, and apolymer selected from the group consisting of gelatin and polyvinylalcohol.

4. A process as defined in claim 1, wherein said photosensitive emulsionis coated over said image-receiving layer on a common support.

References Cited in the file of this patent UNITED STATES PATENTS2,182,794 Dawson Dec. 12, 1939 2,328,034 Sease et al. Aug. 31, 19432,614,926 Land Oct. 21, 1952 2,647,049 Land July 28, 1953 2,707,150 LandApr. 26, 1955 2,774,668 Rogers Dec. 18, 1956 2,842,049 Delangre July 8,1958 OTHER REFERENCES Mees: The Theory of the Photographic Progress,revised edition, pages 87-92, The Macmillan Co., New York, 1954.

1. A PROCESS OF FORMING SILVER DIFFUSION TRANSFER IMAGES WHICH COMPRISESTHE STEPS OF DEVELOPING AN EXPOSED PHOTOSENSITIVE SILVER HALIDE EMULSIONBY CONTACT OF SAID EMULSION WITH AN AQUEOUS ALKALINE PROCESSING SOLUTIONWHICH INCLUDES A SILVER HALIDE DEVELOPING AGENT AND A SILVER HALIDESOLVENT; CONTACTING UNEXPOSED AND UNDEVELOPED SILVER HALIDE THEREIN WITHSAID SILVER HALIDE SOLVENT AND FORMING THEREBY AN IMAGEWISE DISTRIBUTIONOF SOLUBLE SILVER COMPLEX IS UNEXPOSED AREAS OF SAID EMULSION, AS AFUNCTION OF THE POINT-TO-POINT DEGREE OF EXPOSURE THEREOF; TRANSFERRINGFROM SAID EMULSION, AT LEAST IN PART, BY IMBITION, SAID IMAGEWISEDISTRIBUTION OF SOLUBLE SILVER COMPLEX TO AN IMAGE-RECEIIVING LAYERCONTAINING SILVER PRECIPITATION NUCLEI POSITIIONED IN SUPERPOSEDRELATIONSHIP WITH SAID EMULSSION, SAID IMAGE-RECEIVING LAYER CONTAININGDEACETYLATED CHITIN IN A CONCENTRATION SUFFICIENT TO RENDER SAIDIMAGE-RECEIVING LAYER SUBSTANTIALLY WATER INSOLUBLE UPON REACTION OFSAID DACETYLATED CHITIN WITH SAID AQUEOUS ALKALINE PROCESSING SOLUTION;AND THERE PRECIPITATING SAID SILVER COMPLEX TO PROVIDE THEREBY A SILVERTRANSFER IMAGE.
 2. A PROCESS AS DEFINED IN CLAIM 1, WHEREIN AN ADDITIVECOLOR SCREEN IS POSITIONED BETWEEN SAID IMAGE-RECEIVING LAYER AND ASUPPORT FOR SAID IMAGE-RECEIVING LAYER, AND EXPOSURE OF SAIDPHOTOSENSITIVE EMULSION IS EFFECTED THROUGH SAID ADDITIVE COLOR SCREEN.